Heat treatment of permanent magnets



HEAT .lfllfltl'l 01L? PERMANENT MAGNJEAEEA.

No Drawing. Application filed March 21, 1-025, Serial No.1 17,440, and in Great Britain March 25, 11024.

The presentinvention relates to a method of making permanent ma from metal melted in a crucible, or by a process which does not add materially to the 5' carbon contents of the metal, and heat treatment before magnetizing.

According to this invention the heat treat-.

prior patent specification No. 1,464,740 (Reto issue No. 15,847). The characters are then softened, hardened and magnetized.

, As an example, the following heating treatment is adoted when steels containmg cobalt are use for the magnets. A preferred steel is one containing 9 to 15 per cent of cobalt and 9 to 15 per cent of chromium, but any steel usually known as cobalt steel may be employed. .'lo soften the castings they are raised to a temperature of approximately 650 degrees (3., and the heat maintained for abopt half-an-hour when they are allowed to coo The hardening treatment consists of three successiveheatings and coolings before magas netizing. -'lhe first heating is to approxi- -mately 1,200 degrees (3., after which the castings are cooled 0d and allowed to remain for about 18 hours. In the second treatment the castings are re-heated to approximately 750 40 degrees (1, and they are again allowed to cool. lhe castings are then linall heated to approximately 1,000 degrees U, or about ets by casting lln applying the'invention to the manuten minutes and again allowed to cool. It

is preferable to let the castings remain for about twelve, hours after the final heating process before magnetizing. After magnetizing they will be found to be permanent magnets.

Although the invention has been described applied to the manufacture of letters or characters for display devices, it will be understood that it can be employed for making permanent magnets for any other purpose.

What we claim is v 1. A method of making permanent magnets by casting and heat treating the castings only before magnetizing, in which the castings are softened by heating and then hardened by first heating to approximately 1,200 (I, then cooling and leaving for about W 18 hours, reheating to approximately 750 0., and allowing to cool and finally heating to approximately 1,000 C. for ten minutes,- allowing to cool, and leaving for about 12 hours before magnetizing.

2. A method of making permanent mag nets by casting cobalt steel and heat treating the castings only before magnetizing, in which the castings are softened by heating to approximately 650C. andmaintaining the temperature for half-an-hour, then allowing the castings to cool, and then hardened b first heating to approximately 1,200 (if, then cooling and leavlng for about 18 hours, reheating to approximately 750 C. and allowing to cool and finally heating to approximately 1,000 C. for ten minutes, al lowing to cool, and leaving for about 12 hours before magnetizing.

lln testimony whereof we have signed our all names to this specification.

Jaime nnwin can. rannnnrorr SAMUEL one. 

